Artificial sweeteners and other sugar substitutes
Novel sweeteners
Novel sweeteners are hard to fit into a particular category because of what they're made from and how they're made. Stevia is an example. The FDA has approved highly refined stevia preparations as novel sweeteners but hasn't approved whole-leaf stevia or crude stevia extracts for this use.
Tagatose is also considered a novel sweetener because of its chemical structure. Tagatose is a low-carbohydrate sweetener similar to fructose that occurs naturally but is manufactured from the lactose in dairy products. The FDA categorizes tagatose as a GRAS substance.